1. Field of the Invention
The invention relates to off-road light duty vehicles such as lawnmowers and, more particularly, to a suspension system for a ride-on mower.
2. Discussion of the Related Art
Rider versions of self-propelled mowers or “ride-on mowers” are known in the lawn grooming or lawn care industries. Operators of ride-on mowers can mow for relatively long periods of time, since the operators are seated during use. Despite being seated while mowing, operating ride-on mowers can be physically demanding because the operators can be exposed to shocks, vibrations, or other loads, that are generated by the ride-on mower during use or that result from driving the ride-on mower across uneven terrain. Such vibrations, or shock-type or other loads, can transmit through the ride-on mower chassis, foot rest, seat, and controls, and into the legs, bodies, and arms of the operators. For the sake of convenience, these loads that are transmitted to the operator by or through the mower are simply referred to as “shock loads” herein for the sake of brevity.
Various attempts have been made to reduce the imposition of shock loads to operators by using suspension seats that are suspended by springs and/or dampers to isolate the seats from the chassis. However, such seat suspensions fail to reduce transmission of vibrations, or shock-type or other loads, through non-seat components. Accordingly, seat suspensions leave operators susceptible to exposure of shock loads through foot rests, controls, or components other than the seat that are in contact with the operator.
U.S. Patent Application Publication No. 2006/0290080 (the '080 application) discloses a ride-on mower that partially alleviates these problems by providing a platform that is isolated from a chassis by springs at each corner of the platform. The operator's seat is mounted on the platform, and the front portion of the platform serve as an operator footrest. While this system reduces the imposition of shock loads to the operator's feet, the corner mounted springs allow the platform to roll about a longitudinal axis, yaw, and transversely sway, to an extent permitted by a pair of hinges at the front of the platform and a stabilizer bar at the back of the platform. Despite being limited to some extent by the front hinges and back stabilizer bar, such partially limited movements may lead to oscillations of the platform relative to the chassis during certain operating conditions or may be perceived by an operator as being an undesirably loose connection between the platform and chassis. In addition, the steering levers are mounted directly to the chassis, whereby relative movements between the platform and chassis result in relative movements between an operator and the steering levers. Such relative movements between the operator and steering levers can give the steering levers a meandering feel during use, which may not be desirable. Furthermore, mounting the steering levers directly to the chassis allows vibrations, or shock-type or other loads, which are transmitted through the chassis, to also be transmitted through the steering levers and into the arms of the operator.
Yet other attempts have been made to reduce the imposition of shock loads to an operator by using chassis suspension systems that support the entire chassis, from wheels in a manner that is somewhat analogous to an automobile suspension. These systems usually take the form of a system of springs supporting the chassis on the wheels. Such chassis suspension systems are complex, expensive, and require substantial maintenance. They also must be sufficiently robust to support the entire chassis and everything supporting on it, including the seat, the operator, the mower deck, the drive train, etc. They also allow the mower deck to move with respect to underlying ground surfaces. This relative movement can lead to reduced cutting performance. For example, during rapid deceleration occurring during a braking event, the mower deck may “nose dive” or pitch downwardly further into the grass, resulting in “scalping” or an undesirably short cut during the nose-diving occurrence.
Typical suspension systems also provide non-adjustable stiffness deemed to be ideal for a “typical” operator weight. Of course, operators' weights vary dramatically, and even operators' of a given weight may have differences of opinion as to what is considered to be an ideal stiffness under prevailing operating conditions, which may themselves vary. For example, a given operator may prefer a stiffer suspension on smooth terrain than on a rougher or uneven terrain. Traditional suspension systems cannot accommodate these changing needs.
Prior art lawnmowers and other vehicles having suspension systems also tend to have relatively high centers of gravity, reducing the stability of the vehicles.
Many of the problems discussed above are also experienced by other light utility vehicles, such as all terrain vehicles having dumping load carrying beds. One such vehicle is manufactured by John Deere & Co. under the trade name Gator.